Automated institutional and industrial ware-washing machines are generally configured with a single wash tank. The wash tank maintains a readily available supply of a cleaning solution for use in the machine. During normal usage all or a portion of the used cleaning solution is discarded at regular intervals to keep the remaining solution as clean as possible. At the same time fresh or clean recycled water is added to the wash tank to replace the discarded cleaning solution and maintain a constant liquid level. Addition of the fresh water reduces the concentration of detergent or other cleaning composition in the cleaning solution. To maintain the cleaning solution at the most efficient concentration, a measured amount of a concentrated cleaning solution is periodically added to the wash tank by an auxiliary dispenser to form a cleaning solution of the desired strength in the wash tank.
Automated institutional and industrial ware washing machines may also be constructed to add a rinse aid to the rinse water used therein by means of an auxiliary dispenser. The rinse aid promotes sheeting of the rinse water to reduce spotting on the washed ware.
Automated institutional and industrial fabric washing machines typically create a fresh cleaning solution for each cleaning cycle to which is added such cleaning compositions as detergents, bleaches, fabric softeners, and combinations thereof. Typically these cleaning compositions are added to the cleaning solution by auxiliary dispensers.
Chemical dispensers used in the processes described are typically designed for automatic or semi-automatic operation. Automatic dispensers eliminate the need for constant operator attention to cleanliness of the wash water and concentration of cleaning compositions in the wash tank. Further, automated dispensers minimize operator error due to misjudgment in timing or amount of cleaning composition to be added, and provide greater accuracy in maintaining the optimum concentration of cleaning composition in the system.
A number of different techniques have been developed and used for converting a solid cleaning composition into a concentrated cleaning solution. The majority of such devices have been designed to convert solid detergent. See for example Daley et al, U.S. Pat. No. 3,595,438, issued July 27, 1971; Moffet et al, U.S. Pat. No. 4,020,865, issued May 3, 1977; and Larson et al, U.S. Pat. No. 4,063,663, issued Dec. 20, 1977. For this reason cleaning composition dispensers will be further discussed with respect to the dispensing of detergents.
One detergent dispenser technique for converting powdered detergent, is the so-called "water-in-reservoir" type. In the water-in-reservoir type dispensers, an excess of powdered detergent is completely submerged in water to form a saturated concentrated detergent solution having undissolved detergent particles at the bottom of the reservoir. A stand-pipe, usually located near the center of the reservoir, maintains a constant concentrated solution level within the reservoir. As water is injected into the reservoir, a concentrated, often saturated detergent solution or slurry is formed by agitation of the powdered detergent. The added water also causes a portion of the solution or slurry in the reservoir to flow into the stand-pipe, which supplies the wash tank of the washing apparatus with the concentrated detergent solution. Such techniques are not practical for use with powdered detergents containing incompatible components (such as an active chlorine source in combination with a defoamer) as they tend to react upon contact when in solution. Further, there are possible safety hazards involved with the use of such dispensers. The addition of detergent into water-in-reservoir type dispensers requires an operator to place detergent directly into concentrated detergent solution. Since water-in-reservoir type dispensers are typically mounted at about eye level or higher, any splashing or splattering caused by adding the detergent directly into the concentrated solution poses the danger of splashing concentrated detergent solution onto the eyes, face and skin of the operator. This is particularly hazardous when the detergent is highly alkaline or contains other such hazardous chemicals.
Another technique for converting a powdered detergent into a concentrated detergent solution involves the technique of pouring the powdered detergent onto a screen having a mesh size smaller than the powdered detergent particles. A concentrated detergent solution is formed by dissolving the powdered detergent with a spray of water from a nozzle placed on the opposite side of the screen. The concentrated detergent solution formed by the action of the water falls by gravity into an underlying reservoir, or is directed by a conduit directly to the wash tank of a washing apparatus. (See, for example, U.S. Pat. Nos. 3,595,438 issued to Daley et al; 4,020,865 issued to Moffat et al; and 4,063,663 issued to Larson et al.) This technique solves many of the problems associated with the water-in-reservoir type of dispenser as (i) the entire charge of powdered detergent is not wetted, (ii) an operator loading detergent into the dispenser is not placing detergent directly into standing water and therefore is not subjected to possible boil-over or splattering of the concentrated detergent solution, and (iii) the concentrated detergent solution can be used immediately upon being formed, reducing interaction between incompatible components.
While the powdered detergent dispensers such as described by the Daley, Moffat and Larson patents have represented significant contributions to the art of detergent dispensing, the use of powdered solid detergent in general has a number of drawbacks in commercial applications. Due to increased sanitary standards and demands for shorter wash times, recently developed detergents are more complex, increasingly hazardous to the user, less stable, and more difficult to dissolve in a satisfactorily uniform manner. Powdered detergents generally dissolve readily because of their high specific surface areas. However, when the powdered detergent includes components having relatively different dissolving rates, the detergent is susceptible to differential solubility problems in automatic detergent dispensers. Those particles having a greater rate of solubility and/or a greater specific surface tend to dissolve first, whereas those having a lower solubility rate and/or a lower specific surface tend to dissolve last. The extent of this problem depends upon the rate of dispensing and the residence (dwell) time (time of contact between the detergent powder and the dissolving liquid).
Another problem associated with powdered detergents is the incompatibility and/or instability of some useful detergent components when combined in a powdered detergent composition.
Still another problem inherent to powdered detergents is segregation of particles during manufacturing, shipping and handling. Even when uniform distribution can be achieved during manufacture, subsequent shipping and handling may cause segregation. The segregation can lead to non-uniformity in the composition of the detergent when it is withdrawn from the container.
A further disadvantage of powdered detergents is that they are quite susceptible to spillage.
Another form of solid detergent is the briquette form, comprising pre-shaped briquettes of solid detergent. Dispensing systems for dissolving detergent briquettes are known in the art. See, for example, U.S. Pat. Nos. 2,382,163, 2,382,164 and 2,382,165 all issued Aug. 14, 1945 to MacMahon, and U.S. Pat. No. 2,412,819, issued Dec. 17, 1946 to MacMahon. In the MacMahon systems, the detergent briquettes are dispensed from a modified water-in-reservoir type dispenser wherein a number of the briquettes are stacked in a mesh basket forming an inclined slot across the diameter of the reservoir. The lower-most briquette is completely or partly submerged in the water held in the reservoir. A stream of water is directed against the lower-most briquette which, in combination with the swirling action of the water engaging the lower-most briquette, dissolves the briquette and forms a concentrated detergent solution in the reservoir. A stand-pipe maintains a constant concentrated solution level within the reservoir just as in the water-in-reservoir type dispensers. The primary advantages of using detergent briquettes are that the briquettes are easy to handle and the user can visually determine when the detergent dispenser reservoir requires additional detergent. However, as with the water-in-reservoir type dispensers water is left standing in the reservoir, and a portion of the briquettes are submerged within that water. Accordingly, where there are incompatible components within the detergent briquettes, there can be undesirable interaction therebetween. Further, if the detergent contains a defoamer, that defoamer tends to float to the top of the reservoir during periods of inactivity, forming a slag at the water surface. For these and other reasons, the briquette approach has not attained that degree of commercial success in the conventional institutional and industrial cleansing market as has the powdered approach.
Still another, more recent, form of solid detergent is the "cast" or block form, comprising detergent cast into a solid block within a mold or container. Dispensing systems for these solids are known in the art. See, for example, U.S. Pat. Nos. 4,426,362, 4,569,781 and 4,569,780. The cast detergent is typically dispensed in the form of a concentrated detergent solution formed by spraying a dissolving solvent, typically water, onto the detergent block. The concentrated detergent solution is directed into an underlying reservoir or is directed by a conduit directly to the wash tank of a washing apparatus. When the detergent block is completely utilized, the exhausted container is simply removed and a fresh charge placed in the dispenser.
The use of solid cast detergents has presented great innovations to the dispensing of chemicals used in the cleaning process but additional features have been sought by users of solid block dispensers including (i) the ability to provide a relatively constant dispensing rate, (ii) a reduced unit cost of the composition, (iii) further convenience, and (iv) additional safety.
Containers utilized for storing and dispensing of solid cleaning compositions depend upon the form of the composition. Flaked or granular compositions are typically packaged in sturdy paper board containers treated to prevent the passage of moisture into the package. Typically, the granular composition is dispensed from the box by either (i) ripping a hole in the box or (ii) opening a reclosable spout provided on the box. This type of container is unsuitable for nonflowing, solid block cleaning compositions.
Solid cast cleaning compositions are preferably cast directly into a sturdy solid plastic container which can act as a mold, a shipping and storage container, and a dispenser housing. The cast composition is typically dispensed by inverting the container over a fixed position spray nozzle and impinging a dissolving spray onto an exposed surface or surfaces of the compound contained within the container.
Accordingly, a need exists for a dispensing apparatus which can simply, safely, efficiently and inexpensively dispense a homogeneous, uniform, concentrated cleaning solution from a solid block of a cleaning composition; the concentrated cleaning solution dispensed at a substantially constant concentration during the lifetime of the cast cleaner. In certain applications, an additional need exists for an inexpensive solid block chemical container which minimizes the possibility of skin contact with the cleaning composition.